Battery Propulsion System problems of the 2015 Chevrolet Volt

I had my 2015 Volt (at ~95000 miles) serviced at american Chevrolet(modesto, CA) on June 19th for regular maintenance. I had 2 miles ev charge left leaving dealership parking. 2 min out of dealership, just before stopping at a red traffic light, I saw an error: "propulsion power is reduced" on display. Then I realized the car had no power at all. Turned off engine, and turned it back on, the screen says "initializing. . . . . " and it lasted more than 20 seconds, still no power. All cars were moving again, and I was stuck on the second to the right lane with no power! I power cycled again, still no power. Emergency lights didn't light up during initialization. This meant cars behind me wouldn't see my lights. I have a camera facing the rear, and it should have caught the horrific experience. Now came the scary part, I saw a big SUV driving at probably 60mph came right behind me!! luckily the SUV was able to brake really hard and swerved to my right lane before rear ending me. I got out the vehicle, and started signaling to cars behind me, and all the cars now could see me and changed lanes. I called dealer, and two advisors arrived in just a few mins. They could not figure out why and gave me a ride back to dealership and told me the car would be towed back and diagnosed. My Volt has been still at the dealership being test since June 19th. Today, June 24th, my chevy advisor, juan moreno called said they've done all tests, and everything has been fine, and they would do some more testing, after which I should be able to pick it up today. On June 19th, I received a letter from gm about a software update, hpcm2. I requested dealer perform the update. I don't know if the software defect caused my Volt losing power. But now I really had concern over the safety of the Volt as it was a family car to haul family.